Ladder



Feb. 27, 1934. J. E. KALGREN LADDER Filed April 6', 1932 //7 yen for JOHN E. KALGEEN %/5 Afforneys %f m Patented Feb. 27, 1934 UNITED STATES.

LADDER John E. Kalgren, Minneapolis, Minn., assignor to J. K. Clark Company, Minneapolis, Minn., a corporation of Minnesota Application April 6, 1932. Serial No. 603,481

4 Claims.

My present invention provides an important improvement in ladders and especially in the manner of connecting the rungs to the side rails and trussing or reinforcing the same. General- I 1y stated, the invention consists of the novel devices, construction and arrangement of parts hereinafter described and defined in the claims. The invention also involves an improved process of carrying out or applying the invention above indicated, and hence further consists of the novel manipulations and order of manipulations hereinafter described and defined in the claims. A preferred embodiment of the invention is illustrated in the accompanying drawing wherein like characters indicate like parts throughout the several views.

Referring to the drawing:

Fig. 1 is a view partly in elevation, but chiefly in axial section showing one of the ladder rungs 2o ready for application to the ladder rails;

Fig. 2 shows a rung initially applied to the ladder rails;

Fig. 3 is a view chiefly in plan with some parts sectioned showing the elements of the trussing 25 and reinforcing device disassembled but ready for application;

Fig. 4 is a view chiefly in section but with some parts in full showing a ladder rung applied to the ladder rails and the reinforcing means applied thereto; and

Fig. 5 is an elevation of a portion of a ladder showing the rung and reinforcing means in full elevation.

The ladder rails are indicated by the numeral 6 and the rungs by the numeral 7. The rails 6 are provided with the usual holes 8 affording rung seats; and the rungs '7 have reduced ends 9 that closely fit in the holes 8 but preferably do not extend completely through the same.

As first shown in Fig. l, oblique bolt holes 10 are bored from the outer central portion of the outer reduced ends 9 of the rungs in such way that the holes open at the bottoms of the applied rungs. The rungs thus bored are then inserted in the appropriate holes 8 of the rails 6. When the rungs have been inserted as shown in Fig. 2, long bolts 11 of comparatively small diameter but which will closely fit the holes 10, are inserted from the outer end and through one of the holes 50 10 and thence from the inner end and out through the other oblique hole 10 of the rung, with the intermediate projecting portion of the rod 11 at the bottom of the rung. For co-operation with each truss-forming bolt or headed rod 11, there are two washers 12 and a nut 13. These washers 12 are preferably bulged insuch way that their bulged portions enter the outer ends of the holes or rung seats 8, but do not come quite into contact with the ends of the lungs. One of the washers 12 is, of course, placed against the head of the bolt and the other is loosely applied over the screw-threaded end of the bolt and the nut 13 will be applied to the screw-threadedlend of the bolt and against the last noted washer. In fact, the nuts when tightened will be contained 65 freely or quite within'the concavity of the said last noted washer, so that in the preferred arrangement, both the nuts as well as the bolt heads will not project beyond the washers.

When the nuts 13 are properly tightened on the 7 bolts, the bolts will be tightly drawn up against the intermediate lower portions of the rungs and in view of the downwardly bulged form given to the bolts, they will act as truss rods and, of course, also as means for tightly clamping the rails 7 against the shoulders of the rungs. The dimen sions of the parts noted are such that when the truss rods are tightly drawn up by the nuts, the rails will be tightly clamped between the washers and the shoulders of the rungs before the bulged end portions of the washers can possibly be brought into contact with the ends of the rungs.

In fact, it is not intended that the washers should be drawn against the ends of the rungs at any time, but if that should happen, it would only occur after the proper clamping action has taken place between the rails, the washers and the shoulders of the rungs.

In actual practice, it has been found that ladders of minimum weight and maximum strength can be produced. The rungs will obviously stand very great weight because of the reinforcement produced by the truss-acting bolts or rods, which latter in themselves are strong enough to carry any weight that will ever be put upon the rungs. The rungs therefore, while they give additional strength to support the weight of a person on the ladder, serve chiefly as rail spacing means and foot-engaging surfaces, but of course, the rungs give certain additional strength and add to the rigidity of the ladder structure. While straight rods extended axially through the rungs would materially reinforce the same, they would not have the trussing action of the bent rods nor would they to anywhere near the same extent, resist initial downward bend of the intermediate portions of the rungs. In fact, the bent rods when drawn taut, tend to produce a slight upward intermediate bend of the ladder rungs and therefore resist even initial downward spring of 1m the intermediate portions of the rungs under weight.

While it is possible to vary the order in which the above described ladder can be produced, the most efficient, cheapest and best way of producing the same is as follows:

First, the rungs are turned and the oblique holes 10 are bored therethrough, as shown in Fig. 1; and of course, the holes must be bored in the ladder rails. In the second step, the reduced ends 9 of the rungs are inserted in the holes 8 of the ladder rails with the oblique holes 10 opening at the bottom thereof. Next, after the ladder rungs have been inserted as shown in Fig. 2, the bolts or rods 11 are inserted through the oblique holes of the rungs and with the washers applied as shown in Fig. 4, and the nuts are then applied to the rods and the latter are tightened so as to very firmly clamp the ladder rails between the shoulders of the rungs and the washers. It is an important fact which should be noted that when the nutson the rods are properly tightened, the central portions of the rungs will be sprung or bowed upwardly so that it forms the upper member and the rod the lower member of a truss. This upward springing of the rung is due to the fact that under tension, the rod tends to straighten. The rungs are thus arched and put under tension that resists downward springing action under weight. In Fig. 4, the upward bulge of the rung is indicated by its deviation from a broken horizontal line that touches its crown or uppermost central portion.

, The applied rungs will appear as shown in Fig. 5.

It is important that the rungs be inserted into the holes in the rails before the bolts or rods are applied therethrough, for the ends of the rungs are then so held by the rails that they cannot be split or cracked by the act of forcing the rods through the oblique holes. The rods 11 will fill the holes 10 and the joints between the ladder rails with the rungs and washers will be so tight that water cannot enter or get to the inserted ends of the rungs. The completed ladder is a trussed and very rigid structure and may be made very strong in comparison with its weight. Otherwise stated, this invention provides a very high grade ladder at a minimum of cost and a light-weight ladder with a maximum of strength. In the construction of ladders, all of the rungs thereof will preferably be formed and reinforced as described.

What I claim is:

1. A ladder comprising rails and rungs having reduced ends inserted into holes .in said rails, said rungs having oblique rod passages extending to the ends thereof, and rods passed through the oblique passages of said rungs and provided at their ends with means for clamping the rails onto said rungs,said rods being put under such tension that said rungs will be bowed in a direction reverse to the downward bow of said rods.

2. A ladder comprising rails having rungs inserted into holes in said rails, said rungs having oblique rod passages extending to the ends thereextending obliquely through each end portion and adjacent material of said rung to one side thereof, and a rod extending along one side of the rung and through the oblique passages and hav ing means at its ends engaging the outer sides of the rails over the apertures therein and holding the rod under tension.

4. A ladder having apertured side rails, rungs having end portions shaped to fill the apertures in said rails, each of said rungs having a passage extending obliquely through each end portion and adjacent material of said rung to one side thereof, a rod extending along one side oi the rung and through the oblique passages to points within the confines of the apertures in said rails, andmeans extending within the outer ends of the apertures in said rails and engaging the ends of said rod to close said apertures and hold the rod under tension.

V JOHN E. KALGREN. 

